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If you have 1 week caching on your news module, then it will be saved in a HTML file next time it is accessed and not updated until a week later. This means that any news items you publish after the first viewing will not show up until the week after, when the cache is expired and a new HTML file is saved.
There is nothing the user can do to force an update. The caching is on the SERVER, not in the browser.
Updating system or module preferences will clear the cache completely or for the specified module, respectively.